Scientific Method, Measurement, and Practical Skills
This domain tests how scientific questions are framed and tested, how measurements are made and reported, and how laboratory work is carried out safely and accurately.
Core rules
- The scientific method involves observation, a testable hypothesis, controlled experiment, data collection, analysis, and conclusion. An independent variable is changed; a dependent variable is measured; controlled variables are kept constant.
- SI units include the metre for length, kilogram for mass, second for time, ampere for current, kelvin for temperature, and mole for amount. Prefixes such as milli-, centi-, and kilo- change the unit by powers of ten.
- Choose an instrument with a suitable range and smallest division. Read scales at eye level to avoid parallax error. Record measurements with units and appropriate precision.
- Present data in tables or graphs; plot the independent variable on the x-axis and the dependent variable on the y-axis. Safety requires goggles, careful handling of chemicals, and knowing the location of first-aid equipment.
Worked example
A metal block has mass 50 g and volume 20 cm3. Find its density. Density = mass ÷ volume = 50 g ÷ 20 cm3 = 2.5 g/cm3. The reasoning requires dividing the measured mass by the measured volume and keeping the correct compound unit. If the block were cut in half, its mass and volume would both halve, so its density would remain 2.5 g/cm3.
Traps that cost marks
Do not confuse a hypothesis with a theory; a hypothesis is a testable prediction. Do not record a length as 12 cm if the scale reads 12.4 cm. Avoid parallax by reading at eye level. Do not omit units or mix units such as grams and kilograms in one calculation.
Key points
- Identify independent, dependent, and controlled variables.
- Use SI units consistently and convert before calculating.
- Read measuring scales at eye level to avoid parallax error.
- Density = mass ÷ volume, with a compound unit.